Despite important advances in the treatment of heart failure (HF), >50% of patients die within 5 years of diagnosis at their first hospital admission, and HF remains a leading cause of morbidity, mortality and healthcare expenditure in the United States. With the prevalence of HF expected to increase to 46% by 2030, novel mechanistic insight into HF pathogenesis and strategies to interrupt this progression are a large unmet clinical need. My research has focused on the role of exosomes or extracellular vesicles (EVs) and their cargo RNAs (EV-RNAs) as novel functional biomarkers. We have discovered and validated plasma RNA signatures that correlate with human HF phenotypes such as adverse structural remodeling after myocardial infarction, fibrosis and sudden arrhythmic death. We have shown that many of these plasma RNAs are sequestered within EVs and are a novel mode of intercellular communication. Importantly, many of these EV-RNAs change in parallel in cardiac tissue, modulating complex signaling pathways that may underlie HF pathogenesis. This work affords a unique opportunity to develop i) novel clinically useful biomarkers for improved risk stratification of HF patients; and ii) novel therapeutic targets to interrupt the adverse remodeling process. I now seek to leverage the tools and platforms developed over the past 5 years to move the EV and EV-RNA field in new directions using the flexible R35 grant mechanism. I seek to broadly address the following broad areas of unmet need. 1. Improve the performance (including prognostic/predictive accuracy and coefficient of variance) of plasma RNA biomarkers by more specifically measuring EV-RNAs on validated platforms in biorepository plasma samples from carefully-phenotyped HF and post-MI patients. 2. Determine a functional role for EVs isolated from human HF samples with varied phenotypes in simplified cell culture (iPSC-derived CMs) and organ-on-chip models 3. Leverage a novel murine model of exosome tracking (ExoMap) mouse to determine the functional consequences of exosome targeting in cardiomyocytes and other cardiac cells in murine models of ischemic and non-ischemic HF using single cell nuclear RNAseq. 4. Identify small molecule regulators of EV release/uptake to manipulate EV-mediated signaling in these murine models. 5. Leverage newly identified cellular RNA biomarkers to develop novel conditional siRNA therapeutics that target cardiac hypertrophy, autophagy and fibrosis. The flexibility and latitude afforded by the R35 mechanism will allow me to pursue these high-risk high-reward experiments that seek to address critical gaps in this field and will also provide time for devoting to mentoring of the next generation of cardiovascular disease investigators.